This invention relates to an electro-optic device used for various display devices which display an image having a monochrome and/or colored tone partially light and shade or to an electro-optic device useful for optical valves, shades or screens.
Various electro-optic devices which present or show a peculiar electro-optical phenomenon in a relatively low electric field are well known in the art. Such electro-optic devices can be divided into two groups; one group including so-called crystalline liquids, that is, some of the organic substances presenting mesophase indicating that they are states of material intermediate between the liquid and crystalline states or mixtures of these organic substances and the other group including so-called colloidal liquids which are obtained by dispersing a non-organic crystal such as tungsten oxie and vanadium oxide or an anisotropic crystal such as herapathite in a solvent, a typical one of which is the colloidal liquid on the market named VARAD (made by MARKS POLARIZED CO.).
When an electric field is applied to such an electro-optical material, for instance a crystalline liquid; in one case, it changed its state, that is, it changes from a state of presenting an optical isotropy to a state of presenting an optical anisotropy, and in another case, it changes from the state of presenting an optical isotropy to a state of a molecular turbulent flow thereby to uniformly scatter incident light. In addition, a certain type of crystalline liquid material selectively relfects only the light of a particular wave length upon application of an electric field thereto.
Such peculiar optical properties of crystalline liquid material are utilized in a conventional crystalline liquid display device known in the art. Such a conventional crystalline liquid display device is provided with a plurality of electrodes for optical image-creating, confronted each other, on both side of a crystalline liquid film wherein electric field has been properly selectively applied to these electrodes, thus selectively displaying a part of or the whole of the image, but it has never been tried to present a light and shade portion in the image or to display a plurality of colored images.
Generally, such a conventional electro-optical display device, electrical field is applied to electro-optical material by selecting one or both electrode of a pair of electrode which opposes through electro-optical material, and displaying character or simple figure.
Mr. Schulthess filed U.S. Pat. No. 3,774,195 before the filing date of original application of this application.
In this U.S. Pat. No. 3,774,195 electrode of electro-optical display device is divided into plurality of electrodes and blocking current is applied to said electrodes through control voltage circuit from electric source to be measured. Said control voltage circuit is constructed by standard voltage source, and plurality of standard resistors connected in series each other, and these resistors are elements of external voltage dividing circuit to produce step voltage gradient. Therefore, said standard resistors are elements of determination to flow or not said blocking current supplied from electric source to be measured, so that electric voltage is added to selected electrode only from said plurality of electrodes according to the value of voltage to be measured. Therefore principle of this patent is same to prior known electro-optical display device having switching circuit for selecting electrode.
The present invention is to provide electro-optical display device based on different principle from said patent. In this invention, its electrode is divided into a plurality of parts, each electrode is connected at least one external impedance element in series, the impedance ratio between impedance of external impedance element and impedance between electrode in cell differs each other and produce voltage gradient in electrodes in cell, divided currents supplied from external AC electric source flow constantly in all of a plurality of said series circuit, characterized in that the voltage between each first electrode and second electrode differs each other.